The present invention is in the technical area of internal combustion engines, and relates in its category to a control valve for controlling pressure medium flows, having an integrated check valve.
In internal combustion engines having mechanical valve control, gas exchange valves are actuated by a camshaft driven by a crankshaft, the control times of the gas exchange valves are definable via the arrangement and shape of the cams. The use of special devices for the optional modification of the phase position between the crankshaft and the camshaft, generally known as “camshaft adjusters,” has long been known. Through the use of camshaft adjusters, the control times of the gas exchange valves can be influenced in a targeted manner as a function of the momentary operating state of the internal combustion engine, and in this way a number of advantageous effects, such as reduced fuel consumption and reduced production of pollutants, can be achieved.
In general, camshaft adjusters comprise a drive part, which stands in driven connection with the crankshaft via a drive wheel, and an output part connected fixedly to the camshaft, as well as an adjustment mechanism, connected between the drive part and the output part, that transmits the torque from the drive part to the output part and enables an adjustment and fixing of the relative rotational position between the two. In hydraulic camshaft adjusters, the adjustment mechanism comprises at least one pressure chamber pair whose members act against one another, via which the rotational position between the drive part and the output part can be adjusted or fixed by charging the pressure chambers with pressure medium.
As a rule, hydraulic adjustment mechanisms comprise an electronic control device that regulates the inflow and outflow of pressure medium on the basis of acquired characteristic data of the internal combustion engine, using an electromagnetically activated control valve. In a typical design, the control valves have a cylindrical valve housing and a control piston that is axially displaceable inside the valve housing, the piston being displaceable by an electromagnetically movable tappet against the spring force of a resetting spring element. Such control valves are well known, and are described in detail for example in German patent DE 19727180 C2, German patent DE 19616973 C2, and European patent application EP 1 596 041 A2 of applicant.
Mechanically actuated gas exchange valves are as a rule held in the closed position by valve pressure springs. This has the result that when the gas exchange valves are actuated, during opening the cams are pressed opposite the direction of rotation of the camshaft, and during closing they are pressed in the direction of rotation of the camshaft, by the valve springs. Thus, during operation of the internal combustion engine alternating moments occur at the camshaft that can be introduced, as pressure peaks or pulsations, into the pressure medium circuit of the hydraulic adjustment mechanism of the camshaft adjuster. If additional hydraulic components are connected to the pressure medium circuit, these pressure peaks can cause these components to be adversely affected or damaged.
In order to prevent this, it is known to provide check valves in the pressure medium paths of hydraulic camshaft adjusters, which valves block the return flow of pressure medium to the pressure medium pump. The check valves, typically ball check valves, can in particular be integrated in the control valve.
A control valve of the type described having an integrated check valve is described for example in the above-named European patent application EP 1 596 041 A2 of applicant.